First spotted getting cozy while aboard Steven Spielberg's yacht in Monte Carlo on May 17 during the Cannes Film Festival, the couple embarked on a whirlwind, super-luxe summer romance that spanned the globe. During their time together, the Gossip Girl actress, 24, and Inception star, 36, took their PDA parade to romantic locales ranging from Venice, Italy to Anaheim, Calif. to NYC. In late August, Lively even flew thousands of miles from the U.S. to Sydney, Australia -- for a quick weekend -- where her beau was filming The Great Gatsby.

Weeks before he and Lively became an item, DiCaprio and model Bar Refaeli called it quits on their on-and-off, five-year relationship. Back in October 2010, Lively and Gossip Girl costar Penn Badgley ended their three-year romance.

The pair's recent split is sure to come as a surprise to some DiCaprio pals, one of whom told Us they'd "never seen him like this with a girl." Back in June, the couple were ensconced in DiCaprio's L.A. home, where Lively "spent the whole time baking....Leo's never dated a girl who can cook. And he's smitten!" The duo also bonded with one another's parents.

Echoed another insider this summer: "I bet they get engaged in six months."

As for Lively, she's long said she never lets public opinion affect her relationships.

"I have a strong sense of myself. That gives me a sense of security, you know? Every relationship you have, you're learning and growing and taking something from that," the actress recently told Glamour magazine. "So for me, it's never been too dramatic of a thing when something ends."